Is there any precedent or standard means of dealing with co-tenant to co-tenant harassment? my roommate (we're both oin the lease of a rent-stabilized apartment) has threatened to shut off utilities, threatened to sue me over utilities (even though i pay on time), told me i'm not allowed to use the phone, and has been talking about not paying his rent -- since i'd either have to cover the difference or be evicted along with him. he's also had friends over calling me a slut and leaving vulgar messages about me on kitchen blackboards.

any suggestions? is any of this actionable, or just crappy stuff i'll have to put up with or leave?